ARM: S3C: move timer/pwm handling from plat-s3c24xx to plat-s3c

The s3c64xx devices use the same hardware core as s3c24xx, so move
the timer/pwm handling to plat-s3c so it can be used by both.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>